From Fensome et al., 2019:
Impletosphaeridium laxabaculum (Song Zhichen in Song Zhichen et al., 1985, p.31–32, pl.4, fig.11) Islam, 1993, p.86. Holotype: Song
Zhichen et al., 1985, pl.4, fig.11. Originally Cleistosphaeridium, subsequently (and now) Impletosphaeridium. Age: ?Early Pleistocene.

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